40. Escherichia 



Several dozen strains of Escherichia have been studied. Most 

 of these were from the collection of Dr. MacDonald Fulton and 

 included all the common physiological types of Escherichia coli, 

 Escherichia freundii, and the slow lactose fermenting paracolons. 



Flagellar Characteristics 



All strains showed peritrichous arrangement of the flagella 

 (Fig. 42). The flagellation of the colon bacilh is quite variable 

 with atrichous and poorly flagellated strains very common. With 

 most motile cultures the flagellation can be greatly improved by 

 culture in semisolid agar and fishing from the periphery of the 

 spreading growth: Most strains studied showed normal flagella 

 only. A few strains showed both normal and curly flagellated in- 

 dividuals. Individuals with both normal and curly flagella were 

 extremely rare and in no instance could the normal curvature be 

 changed to the curly by lowering the pH. In this respect the 

 coliforms are like Salmonella but unlike Proteus. Some strains may 

 show a considerable proportion of coiled flagella. 



The mean wavelength of the normal flagella of fifteen strains 

 of Escherichia was 2.74 microns. Only one strain with curly 

 flagella was found and the wavelength was 1.15 microns. In Ta- 

 ble VIII are given the mean flagellar wavelengths of various 

 genera in the enteric group. 



98 



